The present invention relates to testing and calibration systems for production line monitoring equipment. More particularly, but not exclusively, it relates to an apparatus and method for confirming the correct operation of foreign body monitoring equipment.
It is important to ensure that goods leaving a production line are not contaminated by extraneous material. This is particularly the case when the line is producing goods such as foodstuffs or pharmaceuticals. Monitoring systems are therefore used to scan products on the line. Metal detectors are used to scan for metal particles or the like, while x-ray scanning is capable of detecting objects having only a slightly different radiological density or consistency from the product, such as bones in meat products, glass, mineral stones, and some plastics materials such as poly(vinyl chloride).
It is customary to run test samples through these monitoring systems, initially to ensure that the system has been properly set up, and then either at regular intervals or randomly, in order to confirm the correct operation of the monitoring system. The results of these tests are recorded in a log, for instance as part of a quality assurance system. Customers of food manufacturers will frequently insist on auditing such logs and the associated procedures, as part of their effort to ensure that their own customers are not at risk and have no cause for complaint from contaminated foodstuffs and the like.
The test samples generally comprise laminated test cards or test sticks that can conveniently be placed on or attached to individual products on the production line.
Specifications will often require that the monitoring system on a production line must pick up a test sample of a particular size and type, every time that such a sample is run through the system. If it fails to do so, the monitoring system must be taken out of service and re-calibrated or adjusted. This almost certainly involves shutting down the whole production line, however, which is potentially very expensive. It has become apparent that this situation has in some cases tempted operators to log the use of a specified test sample, but to pass through the system a more easily detectable sample (e.g. a 3 mm metal particle, where the specification is to detect a 1 mm particle). This reduces the frequency of shut-downs for recalibration, but will lead to mis-calibrated monitoring systems potentially passing contaminated goods that they should have detected. It is equally possible that the wrong test sample might be used in error; this would also lead to mis-calibrated systems not being discovered and corrected.
Similar issues are encountered for other monitoring and measuring equipment used on production lines. In each case, the accuracy of measurements is being guaranteed, expressly or by implication, and so it is necessary to test the reliability of the measuring equipment by challenging it regularly with a standard of some form. As above, the prospective cost of taking equipment out of service for readjustment can tempt those responsible for the equipment to submit inappropriate standards to ensure that the test is passed, regardless of the condition of the equipment. Equally, an incorrect standard could be submitted as a simple error.
For example, microwave techniques are used to measure the fat content of food products, and so standard test samples must be run through the respective equipment to confirm that the measured fat contents are meaningful. X-ray techniques are used in the pharmaceutical field to determine the mass of powder delivered to a tabletting die or to a powder inhaler. Calibration discs are used to ensure that these measurements are accurate. In each case, it is important to ensure that the correct standards are used, and ideally that this can be demonstrated to a customer or a regulatory body.
It is hence an object of the present invention to provide apparatus for checking the operation of such measuring and/or monitoring systems, which obviates the above problems and provides a reliable record of a testing regime actually put into effect for the system. It is also an object of the present invention to provide a corresponding method for checking such measuring and/or monitoring systems.